Due to disease or insult or other causes, the renal system can fail. In renal failure of any cause, there are several physiological derangements. The balance of water, ions (e.g., Na+, K+, Cl−, Ca2+, PO43−, Mg2+, SO42−) and the excretion of daily metabolic load of fixed hydrogen ions is no longer possible in renal failure. Further, during renal failure, toxic end products of nitrogen metabolism including, for example, urea, creatinine, uric acid, and others can accumulate in blood and tissues.
Several types of dialysis have been devised (e.g., peritoneal dialysis, hemodialysis, hemofiltration, and hemodiafiltration) for the removal of toxic end products of nitrogen metabolism from blood. These types of dialysis rely on diffusion of urea across a membrane and/or enzymatic degradation of urea. However, degradation of urea is problematic in that it produces toxic end products such as ammonium that must be removed and or trapped to ensure that they are not returned to a patient. Often sorbents are employed during dialysis to bind such toxic end products. These sorbents are expensive and add bulk to a dialysis system making them less suitable to being used in portable or wearable applications. Therefore, there is a need for dialysis systems that can remove urea from blood without generating toxic end products.